Metal sub-purlin and metal truss cap for use in roof construction

ABSTRACT

A steel sub-purlin for use in roof construction, the sub-purlin being fabricated using metal roll forming techniques. The sub-purlin has an upper, angled portion, a lower angled portion, a vertical section connecting the upper and lower sections and vertical extensions from said upper and lower angled portions positioned in contact with the vertical section. The ends of sub-purlin are positioned on steel truss caps, the truss caps being used in place of conventional wood nailers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides a metal purlin and truss cap for woodroofs having steel framing.

2. Description of the Prior Art

As noted in U.S. Pat. No. 5,499,480 to Bass, the construction industryhas attempted to reduce the use of wood in residential and lightcommercial developments. This, in turn, will reduce the constructioncosts, minimize the types of maintenance problems associated with wood,such as insect damage and decay and also significantly reduce thepotential damage caused by fire.

A steel framing design for use with wood roofs has been available in theroofing industry for a number of years. In one system, open web steeljoists and joist guides are joined with sheathing, thus utilizing theeconomy and strength of open web steel joists and joist guiders with thelow insulation costs and high diaphragm (shear) capacities of aconventional panelized wood roof. In this type of system, sub-purlins,stability braces and roof decking are connected to the joists with itspre-attached wood nailer while all are on the ground.

The conventional wood nailer is attached to the top chord of the openweb stud joist so that the wood sub-purlins and decking are connected bystandard nailing techniques.

Although the panelized roof system described hereinabove providessignificant advantages over commercial roofing systems comprised almostentirely of wood, the steel framing design still utilizes wood nailersand wood sub-purlins with the attendant disadvantages as notedhereinabove. In addition, the shear strength of a roof system havingwood components is limited.

What is therefore desired is to reduce the number of wood componentsutilized in a steel based, commercial roofing system.

SUMMARY OF THE INVENTION

The present invention provides a steel sub-purlin for use in roofconstruction whereby the use of wood is reduced, the structural strengthof the roof significantly increased and the ability of the roof systemto resist shear forces, such as that produced by earthquakes, isincreased.

The sub-purlin of the present invention is fabricated using metal rollforming techniques and is shaped to have an upper, angled portion, alower angled portion, a vertical section connecting the upper and lowersections and vertical extensions from said upper and lower angledportions being positioned in contact with the vertical section.

A truss cap is also provided that replaces the wood nailer.

The present invention thus provides two steel, cold formed componentsthat significantly enhance the shear strength of roofing structureswhile reducing the disadvantages associated with using wood roofingcomponents.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention as well as otherobjects and further features thereof, reference is made to the followingdescription which is to be read in conjunction with the accompanyingdrawing therein:

FIG. 1 is a simplified perspective view illustrating a metal roofconstruction using the sub-purlin and truss cap components of thepresent invention;

FIGS. 2 a and 2 b is a front elevational view and a top plan view,respectively, illustrating the sub-purlin used in the present invention;and

FIG. 3 is a front elevational view illustrating the truss cap used inthe present invention.

DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a partial perspective view of a frameconstruction of a panelized roof system 8 using the sub-purlin of thepresent invention is illustrated.

The construction is conventional for the most part except for the use ofsteel sub-purlins 10 and steel truss caps 12. The conventional portionof the construction comprises sheathing panel 14, lower steel trussjoists 16, upper steel truss joints 17, braces 18, columns 19, and joistbraces 21. Sheathing panel 14 is fastened to the top, or upper, surface56 of the truss cap 12 using metal fasteners, such as metal screws; thiseliminates the need for a conventional wood nailer.

FIG. 1 a is a side view showing sub-purlin 10 fastened to truss cap 12.

Referring to FIGS. 2 a and 2 b, sub-purlin 10 of the present inventionis illustrated in more detail.

Sub-purlin 10, preferably fabricated using a metal roll forming process,comprises an upper portion 20 having angularly extending sides 22 and24, portion 24 continuing into fold over extension 25, connectingvertical portions 26 and 28, and horizontal top surface portion 30. Analignment groove 32 is formed on the top surface portion 30 to guide andalign the nail point. Sub-purlin 10 further comprises a lower portion 40having angularly extending portions 42 and 44, vertical portions 46 and48 and horizontal lower surface portion 50. As shown in FIG. 2 b,sub-purlin 10 includes tab, or lip, portions 52 and 54 which enables thesub-purlins to be fixedly positioned on the upper surface 56 of trusscap 12.

A front elevational view of truss cap 12 is illustrated in FIG. 3, trusscap 12 comprising upper surface 56, vertical portions 58 and 60 andhorizontal edge portions 62 and 64.

Typical dimensions of a sub-purlin 10 that has been successful used insystem 10 are as follows (dimensions in inches):

-   -   a=3.50    -   b=0.75    -   c=1.50    -   d=1.42    -   e=0.68    -   f=0.20    -   g=0.50    -   h=0.50    -   i=0.41    -   j=93.50    -   k=0.75    -   l=1.25

The sub-purlin 10 is preferably fabricated from 20 gauge galvanizedsteel (the grade of steel and steel thickness (gauge) varies inaccordance with the roof load). Using a sub-purlin made of metalimproves the overall fire resistant capability of the structure,improves roof shear, reduces construction time and eliminates two layersrequired for a conventional sub-purlin.

Typical dimensions of a truss cap 12 that has been successfully used insystem 10 are as follows (dimensions in inches):

-   -   a=2.50    -   b=3.50    -   d=5.12

The truss cap 12 is preferably fabricated from 16 gage galvanized steelthe upper steel truss joist 17 being connected to horizontal edgeportions 62 and 64 with steel pins.

The use of a metal truss cap 12 eliminates the need of a wood nailerwhich, in turn, eliminates the need for drilling holes to accept theconventional wood screws. Further, the use of a metal truss cap allowsthe sheathing panel 14 to be installed on the metal truss cap 12 using aheavy industrial gun to insert large metal screws, thus reducingmanufacturing cost and construction times. It should be recognized,however, that the roof construction of the present invention can be usedwith sub-purlins 10 and wood nailers which would be part of aconventional truss joist.

The sub-purlins, truss cap and sheathing panel roof components shown inFIG. 1 is first assembled on the ground, hoisted above the columns andjoist guiders and then secured to the columns and joist guiders in aconventional manner.

While the invention has been described with reference to its preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its essential teachings.

1. A system for use in roof construction comprising: a frame membercomprising a plurality of vertically extending column members having topand bottom portions and a plurality of brace members positioned betweensaid vertically extending columns; a plurality of truss caps extendingin a longitudinal direction and positioned adjacent the top portions ofsaid columns; and a plurality of sub-purlins extending in a firstdirection substantially perpendicular to said truss caps, saidsub-purlins having end extensions that are positioned in contact withthe top surface of said truss caps.
 2. The system of claim 1 whereinsaid sub-purlins are fabricated from metal.
 3. The system of claim 2wherein said metal is steel.
 4. The system of claim 1 wherein said trusscaps are fabricated from metal.
 5. The system of claim 4 wherein saidmetal is steel.
 6. The system of claim 2 wherein each of said metalsub-purlins are fabricated using a roll formed process.
 7. The system ofclaim 6 wherein each of said sub-purlins comprise a first section havingfirst and second angled portions having first and second end portions,two vertical portions having first and second end portions and ahorizontally extending portion having first and second end portions anda first surface extending said first direction.
 8. The system of claim 7wherein each of said sub-purlins further comprises a second sectionhaving first and second angled portions each having first and second endportions, two vertical portions having first and second end portions anda horizontally extending portion having first and second end portions.9. The system of claim 8 wherein said first end of said first angledportion in said first section is joined to said first end of said firstangled portion in said second section by a vertical member having afirst surface.
 10. The system of claim 9 wherein said first end of saidsecond angled portion in said first section extends as a verticalportion positioned adjacent said first surface of said vertical member.11. The system of claim 10 wherein the first end of said second angledportion in said second section extends as a vertical portion positionedadjacent the first surface of said vertical member.
 12. The system ofclaim 7 wherein a groove is formed in said first surface, said grooveextending along the entire length of the surface.